Common salt (NaCl) is not used as a raw material for preparation of which one of the following compounds?
- A.Bleaching powder
- B.Baking soda
- C.Plaster of Paris
- D.Washing soda
Correct answer
Explanation
The correct answer is C, Plaster of Paris. Plaster of Paris is made from gypsum, not from common salt. When gypsum, calcium sulphate dihydrate (CaSO4·2H2O), is heated to about 373 K, it loses part of its water and becomes calcium sulphate hemihydrate (CaSO4·½H2O), which is Plaster of Paris; it sets hard again when mixed with water and is used for casts and statues. Sodium chloride plays no part in this. Option A is wrong because bleaching powder is made by passing chlorine over dry slaked lime, and the chlorine comes from the electrolysis of brine, a salt solution, in the chlor-alkali process. Option B is wrong because baking soda, sodium hydrogencarbonate, is made by the Solvay process from sodium chloride, water, carbon dioxide and ammonia. Option D is wrong because washing soda is obtained by heating baking soda to get sodium carbonate and then recrystallising it with water, so it too comes from common salt. Exam tip: bleaching powder, baking soda and washing soda come from salt; Plaster of Paris comes from gypsum.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
Read the full explanation →Which one of the following statements is correct?
- A.Urea is produced in liver.
- B.Urea is produced in blood.
- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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Liver cells turn the toxic ammonia released from the breakdown of amino acids into urea through the ornithine cycle, also called the urea cycle.
Read the full explanation →Which one of the following is the correct sequence of passage of light in a compound microscope?
- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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Light passes through the condenser to the specimen, is picked up by the objective lens, travels up the body tube and reaches the eye through the eyepiece.
Read the full explanation →Which one of the following statements regarding haemoglobin is correct?
- A.Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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It binds oxygen at its iron-containing haem groups and carries some carbon dioxide on its protein chains. Each haemoglobin molecule has four polypeptide chains and four haem groups, and each haem iron can hold one oxygen molecule, forming oxyhaemoglobin in the lungs.
Read the full explanation →Which one of the following statements regarding histone proteins is correct?
- A.Histones are proteins that are present in mitochondrial membrane.
- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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They are the proteins around which DNA winds to form chromatin in the nucleus of eukaryotic cells. Histones are small basic proteins, rich in the positively charged amino acids lysine and arginine, which attract the negatively charged phosphate groups of DNA.
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